Nap-surface cleaning with tuned frequency beaters

ABSTRACT

A nap-surface cleaning device includes a plurality of flexible rodlike beaters which oscillate to beat the surface and loosen dirt embedded therein. A motor drives the rods at a beating frequency. The rods are constructed so that their natural resonant frequency is closed correlated with the beating frequency.

United States Patent inventor Thomas K. Cauley Fairlawn Village, Ohio Appl. No. 3,692 Filed Jan. 19, 1970 Patented Oct. 26, 1971 Assignee Bissell lnc.

Grand Rapids, Mich.

NAP-SURFACE CLEANING WITH TUNED FREQUENCY BEATERS 9 Claims, 7 Drawing Figs.

US. Cl 134/6, 15/3, l5/50 R, l5/89 Int. Cl A47l 11/00, A47] 1 1/12 Field of Search 134/6, 34; 15/50 R, 320, 89, 98, 3

[56], References Cited UNITED STATES PATENTS 3,328,829 7/l967 Nighswander I 401/22 X 3,398,422 8/1968 Barry et al. 15/50 R X Primary ExaminerMorris O. Wolk Assistant Examiner-R. E. Serwin AttarneyAndrus, Sceales, Starke & Sawall ABSTRACT: A nap-surface cleaning device includes a plurality of flexible rodlike beaters which oscillate to beat the surface and loosen dirt embedded therein. A motor drives the rods at a beating frequency. The rods are constructed so that their natural resonant frequency is closed correlated with the beating frequency.

PATENTEDUCT 28 I971 SHEET 10F 3 R E V m THOMAS K. CAULEY BY Attorneys PATENTEU B 25 3,615,819

SHEET 30F 3 INVENTOR. THOMAS K. CAULEY Attorneys NAP-SURFACE CLEANING WITH TUNED FREQUENCY BEATERS BACKGROUND OF THE DISCLOSURE SUMMARY OF THE INVENTION The present invention is directed to an improvement in prior structures which provides an increased transfer of mechanical energy to the nap surface.

Generally, the invention is based on the concept of using I flexible cantilevered beater rod means of a known natural resonant frequency together with a beating speed which is correlated to that frequency. The beating device is contemplated for use in a vacuum cleaner, wherein dirt loosened from the rug is removed by vacuum.

DESCRIPTION OF THE DRAWINGS The accompanying drawings illustrate the best mode presently contemplated by the inventor for carrying out the invention.

In the drawings:

FIG. 1 is a' perspective view of a device constructed in accordance with the concept of the invention;

FIG. 2 is a side elevation of the device with parts broken away and in section;

FIG. 3 is a perspective view showing the superstructure of the device with parts broken away and in section;

FIG. 4 is an elevational view of the device with parts broken away and in section;

FIG. 5 is a bottom plan view of the device with parts broken away and in section;

FIG. 6 is a view similar to the left portion of FIG. 4, and showing the motion of the beater rods; and

FIG. 7 is a view similar to FIG. 6, and showing the use of auxiliary upper impingement pads and the motion of the beater rods.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawings, the apparatus embodying the concept of the invention includes a manually operable handle 1, a vacuum chamber 2 secured to handle 1, and a framelike lower housing 3. Housing 3 includes an upper cover 4 and a base portions 5. A vacuum motor 6 draws air into and through chamber 2 from a suitable nozzle 7 which moves over the nap surface 8 during reciprocating translation of the device on suitable wheels. The device thus functions as a vacuum cleaner.

Means are provided to beat nap surface 8 to dislodge dirt therefrom. Such a surface could be a rug, carpet, or the like. For this purpose a plurality of elongated flat cantilevered beater rods 9 are mounted in base 5 for beating against the surface. Rods 9 are disposed transversely to the direction of translation of the device and are positioned in overlapping pairs across nozzle 7. The outer end of each rod 9 is connected through a pivotal superstructure l0 and eccentric mechanism II to the output shaft 12 of a motive means, such as motor 13.

Operation motor 13 will pivotally oscillate each rod 9 about a fixed axis 14 to flexingly beat the rod into engagement with nap surface 8.

In accordance with the invention, a maximum transfer of mechanical energy from motor 13 to nap surface 8 is contemplated, to thereby provide maximum effectiveness of dirt loosening. This is accomplished by correlating the natural resonant frequency of rods 9 with the frequency of oscillating drive of rods 9 about their end mounting axes 14.

The invention contemplates use of rods 9 which are flexible and are made from a suitable elastomeric material or the like, such as rubber, nylon, polyurethane, or an acetal resin homopolymer material known as Delrin.

Normal desired beating frequencies for most nap surfaces are usually in the range of 1,800 -3,000 per minute. Thus, if motor 13 is driven at a known desired speed to provide rod oscillation at a desired speed to provide rod oscillation at a desired given point within that range, the invention contemplates use of rods which have natural resonant frequencies which correspond thereto. The rods used in the device are thus manufactured so that they are tuned" to the desired resonant frequency.

Altemately, with a rod of known shape and characteristics, its natural frequency can be determined and the beating frequency correlated therewith.

In either case, the beating frequency cannot be equal to or greater than the natural rod frequency, because this creates instability in rod action. Thus, the beating frequency must be at least slightly less than the natural rod frequency, with the benefits from the inventive concept decreasing as the difference in frequencies increases. At some point of difference, such as where the beating frequency is only 75 percent of the natural rod frequency, the benefits of the invention will cease altogether. I

As an example, assume that each beater rod is made of Urethane elastomer which has the following characteristics:

p weight density 0.045 lb./in.

S endurance limit stress 800 p.s.i.

E modulus of elasticity 10,000 p.s.i.

L rod length 2.375 inches It can be shown that for an arrowhead shaped rod:

L S AhE l .75

Where A arrowhead tip deflection or flexing amplitude during beating, and h rod thickness.

If the optimum desired A=l .3 l 3, the resultant formula is:

where the l is a constant coefficient in cycles per second. Substituting, then, in the formula:

fn= 3066.6 cpm However, as indicated above, the beating frequency needs to be lower than the above natural frequency to prevent instability of the rod. This amount may vary with conditions, so that if the beating frequency is to be 10 percent lower, it should be 2,760 c.p.m.

By correlating the resonant frequency and the beating frequency, maximum excursion motion of the rod tip from neutral position is obtained. No damping of the excursion motion is created. FIG. 6 shows the contemplated whipping-type rod action.

In some instances, it may be desirable to limit the upward excursion of rods 9 from the horizontal neutral position so that their upward excursion distance is equal to the downward excursion distance to surface 8. For this purpose, and as shown in H0. 7, a relatively flrm substantially incompressible pad 15 is mounted to base 5 above the tip portion of each rod 9. As rod 9 moves upwardly, its flexible tip strikes pad and is thrown downwardly thereby with an increased striking force against surface 8.

It has been found that the concept of the invention provides excellent loosening of even coarse material, such as sand, which is then removed from the beating area by the vacuum apparatus. The flexible tuned frequency rods penetrate deep into the nap, even in sculptured carpets having nap of varying depth. Since rods 9 are spaced from each other, loosened dirt is permitted to rise within the nap in the spaces.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

1. A device for cleaning a nap surface, comprising:

a. a base, i

b. means on said base for supporting the device for reciprocal translation over the nap surface,

c. rod support means on said base, I

d. motive means for driving said rod support means at a beating frequency, 3

e. and flexible beater rod means mounted at the end to said rod support means for flexing oscillatory movement into beating engagement with the nap surface,

f. the construction being such that said beating frequency and the natural frequency of said beater rod means are correlated and so that the former frequency is slightly less than the latter frequency to reduce damping of the excursion motion of said rod means and prevent instability thereof.

2. The device of claim 1 which includes: means to limit the upward excursion distance of the oscillating beater rod means.

3. The device of claim 2 in which saidlir'niting means comprises: a relatively firm pad disposed above said rod means for striking engagement thereby.

4. The device of claim 1 which includes: means to remove dirt from the nap surface after the dirt hasbeen loosened by said rod means.

5. The device of claim 3 which includes: means to remove dirt from the nap surface after the dirt has been loosened by said rod means.

6. The device of claim 1 in which said beater rod means comprises a plurality of spaced beater rods.

7. A method of cleaning a nap surface, comprising:

a. providing flexible beater rod means having a given natural resonant frequency,

b. and oscillatingly driving said rod means against the nap surface at a beating frequency which is slightly less than said natural resonant frequency.

8. The method of claim 7:

a. in which the oscillation of said rod means provides upward and downward excursion from the neutral position,

b. and which includes the step of limiting the upward excursion of said rod means.

9. The method of claim 7 which includes the step of removing dirt loosened from the nap surface by said beater rod means.

i i I i 

2. The device of claim 1 which includes: means to limit the upward excursion distance of the oscillating beater rod means.
 3. The device of claim 2 in which said limiting means comprises: a relatively firm pad disposed above said rod means for striking engagement thereby.
 4. The device of claim 1 which includes: means to remove dirt from the nap surface after the dirt has been loosened by said rod means.
 5. The device of claim 3 which includes: means to remove dirt from the nap surface after the dirt has been loosened by said rod means.
 6. The device of claim 1 in which said beater rod means comprises a plurality of spaced beater rods.
 7. A method of cleaning a nap surface, comprising: a. providing flexible beater rod means having a given natural resonant frequency, b. and oscillatingly driving said rod means against the nap surface at a beating frequency which is slightly less than said natural resonant frequency.
 8. The method of claim 7: a. in which the oscillation of said rod means provides upward and downward excursions from the neutral position, b. and which includes the step of limiting the upward excursion of said rod means.
 9. The method of claim 7 which includes the step of removing dirt loosened from the nap surface by said beater rod means. 